A: Acid.

Ab: Antibody.

Abdominal pain: Crampy abdominal pain that may be seen in amebic colitis; right upper quadrant pain in amebic abscess; severe duodenitis or jejunitis with Strongyloides organisms penetrating the mucosa; pain suggestive of gastric ulcer or appendicitis with anisakid larvae (penetration of gut wall).

ABIF: Avidin-biotin immunofluorescence.

ABO blood group: Classification of red blood cells based on the presence or absence of A and B carbohydrate antigens.

Abscess: Localized collection of pus in cavity formed by dissolution of tissue.

Accessioning: Receipt and recording of specimens delivered to laboratory.

Accole: Early ring form of Plasmodium falciparum found at margin of red cell.

ACE: Angiotensin-converting enzyme.

Acellular vaccine: Vaccine consisting of antigenic parts of cells.

Acetoclastis: The process of splitting acetate into methane and carbon dioxide by some methanogens.

Acetyl-CoA pathway: A pathway of autotrophic carbon dioxide fixation common in obligate anaerobes such as methanogens, homoacetogens, and sulfate-reducing bacteria.

Acetylene reduction assay: A method to determine the activity of nitrogenase. Instead of the natural substrate of nitrogenase, i.e. dinitrogen (N2), acetylene is provided as the alternative substrate for this enzyme. Acetylene (C2H2) is reduced to ethylene (C2H4) during the assay if there is nitrogenase activity. Both substrate and product can be resolved by gas chromatography.

Acicular: Needle-shape.

Acid mine drainage: The process to draw off acidic water from natural mine rich of sulfide minerals which has been oxidized to sulfuric acid by microbial actions.

Acid-fast: The property of resisting decolorization with acidified alcohol or with dilute mineral acids after being stained with a strong dye such as carbol fuchsin.

Acidophile: An organism that grows optimally at acidic (low) pH values (usually below 6, sometimes as low as 1) and grows poorly or not at all under higher pH conditions (i.e. higher than 7).

Acidophilic: Growing best under acidic conditions.

ACIF: Anticomplement immunofluorescence.

Acquired immunodeficiency syndrome (AIDS): Serve immune deficiency disease caused by human immunodeficiency virus (HIV-1) infection of the T cells, characterized by opportunistic infections and other complications.

Acrogenous: Borne at the tip of a conidiophore.

Acropetal: Produced in succession toward the apex (youngest conidium at the tip).

Actinomycetes: Gram-positive bacteria that can form branching filaments. They may form true mycelia or produce conidiospores.

Activation energy: Energy required to make substrate molecules active enough for a reaction to occur. Catalysts and enzymes function by lowering the activation energy of the substrates during a chemical reaction.

Activator: A regulatory protein that binds to specific sites on DNA and stimulates transcription; an activator is usually involved in the positive control of transcription regulation.

Active immunity: Production of antibodies by the body's own immune system due to the exposure to antigen. Compare with passive immunity.

Active site: The region of an enzyme where substrate(s) bind(s) prior to the reaction occurring.

Active transport: The energy-dependent process of transporting substances (e.g. nutrients, ions, waste products) into (uptake) or out of (efflux) the cell in which the transported substances are chemically unchanged.

Acuminate: Tapering to a narrow tip.

Acute: Used to describe a short-term infection or disease which is characterized by dramatic onset and rapid recovery.

Acute abdomen: An abdominal condition of abrupt onset usually associated with abdominal pain resulting from inflammation, perforation, obstruction, infarction, or rupture of intra-abdominal organs; surgical intervention is usually necessary (ascariasis, anisakiasis).

Acute serum: Serum collected for antibody determination early in course of an illness when there would have been little or no antibody produced.

Acute urethral syndrome: Lower urinary tract infection that may be difficult to differentiate from cystitis; seen most commonly in younger, sexually active females and caused by Escherichia coli (counts as low as 100 per milliliter may be significant in this situation), Chlamydia, and other organisms.

ADA: Americans with Disabilities Act.

Adenopathy: An enlargement of lymph nodes in response to some stilulus such as inflammation or infection; can occur singly or in multiple nodes; also referred to as lymphadenopathy.

Adenosine triphosphate (ATP): The principal energy carrier of the cell.

Adherence: Refers to the ability of bacteria to adhere (stick) to host surfaces.

Adiaconidium (pl. adiaconidia): A conidia that greatly enlarges in the host or at high temperatures without reproduction.

Adnexa: An apppendage to an organ or structure.

Adrenalitis: Inflammation of the adrenal gland.

AE: Agarose electrophoresis.

Aerial hyphae: Hyphae above agar surface.

Aerobe: An organism that is capable of using oxygen as a terminal electron acceptor, can tolerate a level of oxygen equivalent to or higher than that present in an air atmosphere (21% oxygen), and has a strictly respiratory type of metabolism. Some aerobes may also be capable of growing anaerobically with electron accepters other than oxygen.

Aerobic: Able to grow in the presence of atmospheric oxygen.

Aerogenic: Gas production, e.g., aerogenic fermentation.

Aerosol: Atomized particles suspended in air; in context of this book, microorganisms suspended in air.

Aerotolerant: Ability of an anaerobic microorganism to grow in air, usually poorly, especially after initial anaerobic isolation.

Aerotolerance testing: A procedure used to determine the atmospheric requirements of an isolate suspected of being an anaerobe.

AFB: Acid-fast bacilli.

Afebrile: Relating to the absence of fever.

Affinity: Inherent attraction and relationship.

Ag: Silver, Antigen.

Agar: A complex polysaccharide which is widely used as a gelling agent used to prepare solid or semi-solid microbiological medium. Agar consists of about 70% of agarose and 30% agaropectin. Agar can melt at temperatures above 100 degrees C; gelling temperature is 40-50 degrees C. Also called: agar agar.

Agarose: A non-sulphated linear polymer consisting of alternating residues of D-galatose and 3,6-anhydro-L-galactose:
[-3,6-anhydro-alpha-L-galactopyranosyl-(1->3)-beta-D-galactopyranosyl-(1>4)-]n

Agarose is extracted from seaweed and is widely used as the resolving agent in electrophoresis (i.e. agarose gel electrophoresis).

Agarose gel electrophoresis: Separation of proteins based on molecular weight by electrical-currentstimulated movement through a semisolid gel matrix.

Agglutination: Aggregation or clumping of particles, such as bacteria when exposed to specific antibody.

AIDS: Acquired immunodeficiency syndrome.

AIDS-related complex (ARC): Prodromal symptoms in patients infected with HIV virus, including lymphadenopathy, fever, weight loss, and malaise.

Alae: Pronounced, longitudinal cuticular ridges in nematodes, usually found in larval stages (Ascaris lumbricoides), although occasionally present in adult worms (Enterobius vermicularis).

Aleurioconidium (pl. aleurioconidia): A terminal or lateral conidium developed by expansion of the end of a conidiophore or hypha, and detaches by lysis or fracture of the wall.

Alga (plural algae): Phototrophic eukaryotic microorganisms. Algae could be unicellular or multicellular. Blue-green algae is not true algae; it belongs to a group of bacteria called cyanobacteria because it lacks a nucleus in the cell.

ALK (or K): Alkaline.

Alkaliphile (also alkalophile): An organism that grows optimally at high pH (alkaline conditions). The typical pH range for alkaliphiles is 8-11. They grow poorly or not at all at a pH below 7. Compare with acidophile.

Alkaliphilic: Growing best under alkaline conditions.

Allergy: A hypersensitive condition acquired by exposure to a particular allergen (helminth infections; house dust mite or ectoparasite bites or stings).

Allosteric: Used to describe some protein, especially enzymes, in which a compound combines with a site on the protein other than the active site. This may result in a conformational change at the active site so that the normal substrate cannot bind to it. The allosteric property is useful in the regulation of enzyme activity.

Alopecia: Baldness.

Alpha-hemolysis: Reduction of hemoglobin to methemoglobin.

ALT: Alanine aminotransferase.

Alveolus: An air sac in the lung consisting of a single layer of cells surrounded by a network of capillaries also consisting of a single cell layer; gas exchange occurs here.

Amastigote: Small, round, intracellular stage of Leishmania spp. and Trypanosoma cruzi in which the base of the flagellum is anterior to the nucleus but there is no external flagellum; also called Leishman-Donovan body, L-D body, or leishmanial stage.

Amber mutation: The mutation due to the introduction of a stop codon (UAG) within the coding sequence of a gene which results in premature termination of translation.

AMI: Antibody-mediated immune response.

Amino acid: An organic acid containing an amino group (-NH2) and a carboxyl group (-COOH). Can be represented by the general formula: R-CH(NH2)COOH, in which R may be hydrogen or an organic group and determines the properties of the amino acid. Amino acids are building blocks of proteins.

Amino group: -NH2.

Aminoglycosides: Group of related antibiotics including streptomycin, kanamycin, neomycin, tobramycin, gentamicin, and amikacin.

Amniotic: Pertaining to the innermost fetal membrane forming a fluid-filled sac.

Amoeba (or ameba, plural: amoebae): Refers to any (eukaryotic) cell or organism which is able to alter its cell shape drastically, usually by the extrusion of one or more pseudopodia.

Amoeboid: Amoeba-like.

Amoeboid movement: A type of motility in which cytoplasmic streaming extrudes outward of the cell to form pseudopodia so that the cell can be relocated.

Amplification1: Increase of copy number of a plasmid by inhibiting the replication of chromosome while allowing plasmid replication to continue.

Amplification2: Increase of the number of copies of a gene either by duplication in the chromosome or by cloning into a plasmid vector. This is normally referred to as gene amplification.

ANA: See anti-nuclear antibody.

Anabolism: Refers to those metabolic processes involved in the synthesis of cell constituents from simpler molecules, such as organic and/or inorganic precursors. An anabolic process usually requires energy.

Anaerobe: An organism that is incapable of oxygen-dependent growth and cannot grow in the presence of an oxygen concentration equivalent to that present in an air atmosphere (21% oxygen). Some anaerobes may have a fermentative type of metabolism; others may carry out anaerobic respiration in which a terminal electron acceptor other than oxygen is used.

Anaerobic: Able to grow in the absence of free or atmospheric oxygen.

Anaerobic respiration: Respiration under anaerobic conditions. The terminal electron acceptor, instead of oxygen in the case of regular respiration, can be: CO2, FE2+, fumarate, nitrate, nitrite, nitrous oxide, sulphur, sulphate, etc. Note that anaerobic respiration still uses electron transport chain to dump the electron while fermentation does not.

Anaerobiosis: Life in the absence of molecular oxygen.

Anaerogenic: Non-gas-producing.

Analytic reagent (AR): Grade of chemical.

Anamnestic response: More rapid production of antibodies in response to exposure to an antigen previously encountered.

Anamorph: A somatic or reproductive structure without nuclear recombination in the asexual cycle.

Anaphylatoxins: The C3a and C5a fractions during complement fixation. They act to mimic some of the reactions of anaphylaxis and can induce the release of histamine from mast cells. C5a is also chemotactic for neutrophils and monocytes.

Anaphylaxis: Hypersensitivity produced by exposure to further doses of the same protein, usually when exposure is within less than 2 weeks (bee stings, echinococcosis).

Anemia: A reduced number of erythrocytes per cubic millimeter, reduction in amount of hemoglobin, or reduction in volume of packed red cells per 100ml of blood (malaria; hookworm and Diphyllobothrium latum infections).

Anergic: Absence of sensitivity to an antigen or the condition resulting from desensitization (cutaneous leishmaniasis).

Anergy: Absence of reaction to antigens or allergens.

Annealing: The process of formation of double-stranded DNA from single-stranded DNA; compare with hybridization.

Annellide: A cell that produces and extrudes conidia; the tip tapers, lengthens, and acquires a ring of cell wall material as each conidium is released; oil immersion magnification may be required to see the rings.

Annelloconidium (pl. annelloconidia): A conidium formed from an annellide.

Anorexia: Absence of appetite.

Anoxic (noun: anoxia): Lack of oxygen. An adjective usually used to describe a microbial habitat.

Anoxygenic: Not able to produce oxygen. (Contrast with oxygenic).

Anaoxygenic photosynthesis: A type of photosynthesis in green and purple bacteria in which oxygen is not produced. Use of light energy to synthesize ATP by cyclic photophosphorylation without oxygen production in green and purple bacteria.

Antagonism: Diminution of activity of one drug by a second one.

Antheridium (pl. antheridia): Male gametangium.

Anthropophilic: Fungi that usually infect humans only. Example: Microsporum audouinii.

Antibiogram: Distinctive pattern of susceptibility of an organism to a battery of antimicrobial agents.

Antibiotic: Substance, produced by a microorganism, that inhibits or kills other microorganisms; a broad-spectrum antibiotic is therapeutically effective against a wide range of bacteria.

Antibody: Substance (immunoglobulin), formed in blood or tissues that interacts only with antigen that induced its synthesis (e.g., agglutinin).

Anticodon: A sequence of three bases in tRNA that base pairs with a codon in mRNA.

Anticomplement Immunofluorescence (ACIF) is a technique used to make certain indirect fluorescent antibody techniques more specific and sensitive. Here the fluorescent dye is conjugated to antibody directed at complement and then added to a complement-fixing complex of antigen and patient antibody.

Antigen: Molecular structure that is capable of stimulating production of antibody.

Antigen-presenting cell (APC): Cells that process and present antigen to T lymphocytes.

Antigenic determinant: The portion of an antigen that interacts with an immunoglobulin or T cell receptor.

Antigenic drift: In influenza virus, minor changes in viral proteins (antigens) due to gene mutation.

Anti-metabolite: An analogue of the end-product of a metabolic pathway that causes feedback inhibition or repression, but cannot replace the genuine product; used for selecting feedback-deficient mutants.

Antimicrobial: Chemical substance, either produced by a microorganism or by synthetic means, that is capable of killing or suppressing growth of microorganisms.

Anti-nuclear antibody: Anti-nuclear antibody (ANA) is antibody against nuclear materials such as DNA, RNA, histone or non-histone proteins. ANA is usually found in the serum of individuals with certain automimmune diseases, e.g., systemic lupus erythematosus (SLE), Sjogren's syndrome, polymyositis, systemic sclerosis, etc. Different diseases have ANA against different nuclear components.

Antiparallel: In reference to double-stranded DNA, the orientation of the two strands: one strand runs 5'-->3', the other 3'-->5'.

Antiphagocytic: Inhibiting the ability of the phagocyte to ingest bacteria, foreign materials, or other cellular debris.

Antipyretics: Fever-reducing agents such as aspirin, acetaminophen, or ibuprofen.

Antisense RNA: A sequence of RNA which is complementary to the mRNA. Antisense RNA can usually interfere with translation process.

Antiseptic: Compound that stops or inhibits growth of bacteria without necessarily killing them.

Antiserum: A serum containing antibodies.

Anti-terminator: A protein that allows RN polymerase to read through a terminator.

Antitoxin: An antibody that specifically interacts with and neutralizes a toxin.

Anuria: Absence of urine secretion (scorpion sting).

Apex (pl. apices): The tip.

APF: Assigned protection factor.

Aphasia: Partial or complete inability to speak or understand spoken words.

Aplastic anemia: Decrease in the numbers of all elements in the blood due to the death of their precursor cells in the bone marrow, where the cells usually mature; often associated with drugs which are toxic to these cells.

Apiculus: A short projection at one or both ends of a spore or conidium.

Apophysis: The swelling of a sporangiophore immediately below the columella.

Apoptosis: A type of programmed cell death, involving activation of endogenous autolysins and fragmentation of DNA.

Appendicitis: Inflammation of the vermiform appendix (amebiasis; Ascaris, Trichuris, and Enterobius infections).

Appendix: Thick-walled fingerlike projection at the end of the cecum.

Applique: Early ring form of Plasmodium falciparum found at the margin of red blood cells; accole.

Arboviruses: Arthropod-borne viruses.

ARC: AIDS-related complex; Anomalous retinal correspondence.

Archaea: An evolutionarily distinct group (domain) of prokaryotes consisting of the methanogens, most extreme halophiles and hyperthermophiles, and Thermoplasma.

Archaebacteria: An older term for the Archaea.

ARD: Acute respiratory disease.

ART: Automated reagin test for syphilis.

Arthralgia: Severe joint pain, usually characterized as noninflammatory.

Arthritis, septic: Infection of synovial tissue and joint fluid of one or more joints; characterized by joint pain, stiffness, swelling, and fever.

Arthroconidium: An asexual spore formed by the breaking up of a hypha at the point of septation. The resulting cell may be rectangular or barrel shaped and thick or thin walled, depending on the genus.

Ascites: Effusion of serous fluid into the abdominal cavity (schistosomiasis).

Ascitic fluid: Serous fluid in peritoneal cavity.

Ascocarp: A fruiting body containing ascospores.

Ascospore: A sexual spore produced in a sac-like structure known as an ascus.

Ascus: (pl. asci): A round or elongate sac-like structure containing usually two to eight ascospores. The asci are often formed within a fruiting body, such as a cleistothecium or perithecium.

Aseptate: Lacking cross-walls. Example: Rhizopus.

Aseptic technique: Manipulation of sterile instruments or culture media in such a way as to maintain sterility.

Asexual: Reproduction in an organism by division or redistribution of nuclei, but without nuclear fusion, i.e., not by the union of two nuclei. Also known as imperfect state.

ASO: Antistreptolysin.

Aspirate: Fluid removed from a cavity or lesion (leishmaniasis, hydatid disease, amebiasis).

Asplenia: Absence of the spleen, either congenitally (at birth) or later, often seen in persons with long-standing sickling disease. This condition makes the individual susceptible to infections by certain bacteria.

Assimilation: The ability to use a carbon or nitrogen source for growth in the presence of oxygen.

AST: Asparate aminotransferase (formerly SGOT).

Asterixis: An involuntary jerking motion that occurs with carious toxic or metabolic encephalopathies, especially hepatitis encelphaoopathy; most easily demonstrated when the patient is asked to extend his or her arms with the hands pointed up and the fingers extended.

Asthma, bronchial: Disease characterized by difficulty in breathing, wheezing, and coughing caused by spasmodic contraction of the bronchi; may be the result of allergic reaction (ascariasis, strongyloidiasis, visceral larva migrans, house dust mites). Also see Eosinophilia.

Ataxia: The inability to coordinate muscle activity during voluntary movements of the head, limbs, or trunk; often associated with cerebellar or posterior spinal column dysfunction.

ATCC: American Type Culture Collection.

Atomic weight: The average weight of an atom of an element, i.e. the total mass of protons and neutrons in an atom.

Atrophy: A process characterized by wasting of specific tissues, organs , or the entire body that can result from a variety of causes.

Attenuation1: Reduction in the virulence of a pathogen; usually an attenuated pathogen is still capable of immunizing.

Attenuation2: A process that plays a role in the regulation of enzymes involved in amino acid biosynthesis.

Auscultation: A method based on sounds or sound changes, used during a physical examination to gather data on internal organs like the heart, lungs, liver, etc., the most common method involves the use of a stethoscope.

Autoantibody: Antibodies that react to self antigens.

Autochthonous: Indigenous or normally found in a particular area.

Autoclave: Instrument consisting of a double-walled, sealable enclosure in which steam heat at greater than atmospheric pressure is used to sterilize biologically contaminated material.

Autogenous control: The expression of a gene is regulated by its own gene product(s).

Autoimmunity: Immune reactions of a host against its own self constituents.

Autoinfection: Reinfection by an organism already present in the body with an increase in the number of parasites without their undergoing a cycle outside the body; self-infection (Strongyloides stercoralis, Hymenolepis nana, Cryptosporidium parvum).

Autolysis: Spontaneous lysis.

Autopsy: Gross and microscopic postmortem examination of the organs of the body to determine cause of death or pathological changes.

Autoradiography: Detection of radioactivity in a sample, for example a cell or gel, by placing it in contact with a photographic film (e.g. X-ray film).

Autotroph: An organism that used inorganic compounds as nutrients and carbon dioxide as the sole source of carbon. (Contrast with heterotroph).

Auxanographic Technique: A method for determination of carbon or nitrogen utilization by placing the substrate onto the surface of a basal agar medium seeded with a test organism such as a yeast.

Auxotroph: Differing from the wild strain (prototroph) by an additional nutritional requirement.

Avid: The property of binding strongly, such as an antibody that strongly binds to an antigen.

Avidin-Biotin Immunofluorescence (ABIF) holds promise for more sensitive and specific amplification of indirect fluorescent antibody procedures. Antibody to the patient's specific antibodies is labeled with biotin, a compound capable of specifically binding avidin in high concentrations. Fluorescently labeled avidin is then added and fluorescent microscopy is used to detect the presence of the complexes.

Avidity: Firmness of union of two substances; used commonly to describe union of antibody to antigen.

Avirulent: Microorganism with limited pathogenic potential.

Axillus: Armpit; the area between the upper arm and chest wall where the two join.

Axostyle: Rodlike supporting structure in some flagellates that gives rigidity to the body (Trichomonas spp.).